Polylactic acid, polylactic acid spunlace non-woven fabric and application thereof on soft wet wipes

Abstract

The application relates to the technical field of high polymer materials, in particular to a polylactic acid, polylactic acid spunlace non-woven fabric and application of the polylactic acid spunlace non-woven fabric on soft wet wipes. The polylactic acid is prepared from the following components in parts by weight: polylactic acid matrix resin 60-85 parts, polyester elastomer 10-30 parts, reactive end-capped hydrophilic agent 5-20 parts, chain extender 0.3-2.5 parts and nucleating agent 0.1-1.5 parts. The polylactic acid spunlace non-woven fabric is prepared through melt spinning, web laying and spunlace reinforcement of the polylactic acid, and the polylactic acid spunlace non-woven fabric has high dry / wet strength, excellent softness and rapid water absorption characteristics.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to polylactic acid, polylactic acid spunlace nonwoven fabric and its application in soft wet wipes. Background Technology

[0002] With increasingly stringent global environmental regulations and growing consumer demand for sustainable products, bio-based biodegradable materials have become a significant trend in the disposable hygiene products sector, replacing traditional petroleum-based materials. Polylactic acid (PLA), as the most representative bio-based and fully biodegradable polyester material, shows great potential in products such as nonwoven fabrics and wet wipes due to its excellent biocompatibility, processability, and the advantage of being derived from renewable resources.

[0003] However, the large-scale application of polylactic acid (PLA) in soft wet wipes, which require extremely high softness, hydrophilicity, and wet strength, still faces significant technical challenges. First, PLA itself is quite brittle, lacking sufficient flexibility in both dry and wet states, affecting the skin feel and product durability during wiping. Second, PLA's strong hydrophobicity results in slow water absorption and low liquid retention in its nonwoven fabric substrate, making it difficult to meet the requirements of rapid wetting and effective liquid retention in wet wipes. Current technologies often improve performance through blending plasticizers or physically coating hydrophilic agents, but this often leads to a decrease in material strength and a lack of long-lasting hydrophilicity. Furthermore, PLA nonwoven fabrics produced by traditional hot-rolling or spunbonding methods tend to have a stiff feel, while hydroentangling, although giving nonwoven fabrics excellent softness and fluffiness, places more stringent requirements on the strength, hydroentangling resistance, and final hydrophilic uniformity of the fabric surface.

[0004] Therefore, developing a polylactic acid material that combines high flexibility, long-lasting and rapid hydrophilicity, good processing performance, and suitability for spunlace technology, and then preparing spunlace nonwoven fabric that can meet the performance requirements of high-end soft wet wipes, has significant market value and technical significance. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide a polylactic acid, which is prepared by comprising the following components in parts by weight: 60-85 parts of polylactic acid matrix resin, 10-30 parts of polyester elastomer, 5-20 parts of reactive end-capping hydrophilic agent, 0.3-2.5 parts of chain extender, and 0.1-1.5 parts of nucleating agent. The method for preparing the polylactic acid includes the following steps: The reactive end-capped hydrophilic agent, the polyester elastomer, and the chain extender are premixed to obtain a premix; The premixed material is melt-blended with the polylactic acid matrix resin and the nucleating agent, and then extruded, cooled, and pelletized to obtain the polylactic acid.

[0006] Preferably, the polyester elastomer is selected from at least one of polybutylene adipate-terephthalate, polylactic acid-polycaprolactone block copolymer, and polybutylene succinate; the melting point of the polyester elastomer is 80-120°C, and the melt flow rate is 5-50 g / 10 min at 190°C and 2.16 kg load.

[0007] Preferably, the reactive end-capping hydrophilic agent is selected from at least one of the following: polyethylene glycol with single-end epoxy group end-capping, polyethylene glycol with single-end isocyanate group end-capping, polyethylene glycol-polypropylene glycol block copolymer with single-end epoxy group end-capping, polyethylene glycol-polypropylene glycol block copolymer with single-end isocyanate group end-capping, polyethylene glycol with double-end epoxy group end-capping, polyethylene glycol with double-end isocyanate group end-capping, polyethylene glycol-polypropylene glycol block copolymer with double-end epoxy group end-capping, and polyethylene glycol-polypropylene glycol block copolymer with double-end isocyanate group end-capping; the number average molecular weight of the reactive end-capping hydrophilic agent is 1000-3000.

[0008] Preferably, the chain extender is selected from at least one of epoxy chain extenders and oxazoline chain extenders.

[0009] Preferably, the nucleating agent is selected from at least one of microcrystalline cellulose, calcium magnesium phytate, and chitin nanocrystals.

[0010] Preferably, the premixing conditions are: mixing for 20-40 minutes at 50-80°C under nitrogen atmosphere protection; during melt blending, the processing temperature range is 170-190°C and the screw speed is 150-350 rpm.

[0011] This invention also discloses a polylactic acid spunlace nonwoven fabric, which is prepared by spinning, web laying, and hydroentangling reinforcement of polylactic acid as described above, specifically including: S1. Spinning: After drying the polylactic acid, polylactic acid fibers are obtained through melt spinning, winding, stretching and heat setting processes. S2, Web Laying: Laying polylactic acid fibers into a web; S3. Hydroentangling reinforcement: The fiber web is subjected to hydroentangling reinforcement treatment and dried to obtain the polylactic acid hydroentangled nonwoven fabric.

[0012] Preferably, in step S1, the spinning temperature is 190-210℃, the winding speed is 1500-2800m / min, the drawing temperature is 70-95℃, the drawing ratio is 2.2-3.8 times, and the heat setting temperature is 80-105℃; in step S2, the web laying method is cross-laying; and in step S3, the hydroentangling pressure is 80-120 bar.

[0013] Preferably, the polylactic acid fiber in S1 has a single filament fineness of 1.2-2.8 dtex; and the fiber web in S2 has a basis weight of 25-55 g / m². 2 .

[0014] An application of polylactic acid spunlace nonwoven fabric, as described above, in soft wet wipes.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a reactive end-capped hydrophilic agent and a specific polyester elastomer, and premixes and melt blends them in the presence of a chain extender. During the blending process, the reactive groups (epoxy groups, isocyanate groups) at the end of the hydrophilic agent can chemically react with the hydroxyl or carboxyl groups at the end of the polylactic acid (PLA) molecular chain. Simultaneously, the multifunctional active groups in the chain extender molecule can react with both PLA and the hydrophilic agent to form a chemically bonded graft network. This anchors the hydrophilic segments in the polymer matrix via covalent bonds, fundamentally preventing the migration and precipitation of hydrophilic components in an aqueous environment, thus endowing the material with durable and stable hydrophilicity. The chemical bonding interface between the polyester elastomer and the PLA matrix is ​​formed through the bridging effect of the chain extender, which can significantly improve the compatibility and melt strength of the blend, effectively promote stress dispersion and energy absorption, and enable the material to improve toughness without sacrificing mechanical integrity. The introduction of nucleating agents in this invention promotes heterogeneous nucleation of polylactic acid during the spinning and cooling process, forming a finer and more uniform crystal structure, which improves the initial modulus and heat resistance of the fiber. At the same time, through premixing activation and optimized melt blending process, the reactive components are ensured to react fully and disperse evenly. The prepared composite material has high melt strength and stable rheological properties, which enables the smooth spinning of fine denier fibers with uniform fineness and high strength at spinning temperatures of 190-210℃. The fiber web made from this fiber can withstand the impact of high-pressure hydroentanglement without easily breaking or being excessively damaged. The fibers form a stable three-dimensional network structure through hydroentanglement, thus successfully preparing a fully hydroentangled nonwoven fabric with both excellent soft and fluffy hand feel and sufficient dry and wet strength. The polylactic acid spunlace nonwoven fabric prepared by this invention has rapid, uniform and long-lasting water absorption properties brought about by chemically bonded hydrophilic segments, as well as excellent dry / wet softness and toughness endowed by elastomers and optimized fiber structure. When applied to soft wipes, this substrate can quickly absorb and lock in skin care liquid, providing a consistently soft wiping experience, and is not easy to pill or break during use. Attached Figure Description

[0016] Figure 1 The graph shows the results of measuring the monofilament strength and monofilament elongation in the fiber strength test of polylactic acid fibers prepared in Examples 1-3 and Comparative Examples 1-5 of this invention. Figure 2The graph shows the results of measuring the dry and wet strength of the polylactic acid spunlace nonwoven fabrics prepared in Examples 1-3 and Comparative Examples 1-5 of this invention. Figure 3 The graph shows the results of measuring the softness of the polylactic acid spunlace nonwoven fabrics prepared in Examples 1-3 and Comparative Examples 1-5 of this invention. Figure 4 The graph shows the results of liquid penetration time measurement of polylactic acid spunlace nonwoven fabrics prepared in Examples 1-3 and Comparative Examples 1-5 of this invention. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] Example 1: This example provides a method for preparing polylactic acid spunlace nonwoven fabric, including the following steps: Step 1: Preparation of polylactic acid: S1. Weigh the raw materials according to the following parts by weight: polylactic acid matrix resin (brand: 4032D, NatureWorks LLC, weight average molecular weight of 100,000, melt flow rate of 28g / 10min at 190℃ and 2.16kg load): 60 parts; polybutylene adipate terephthalate (melting point of 85℃, melt flow rate of 45g / 10min at 190℃ and 2.16kg load): 10 parts; polyethylene glycol with single-end epoxy groups (number average molecular weight of 1000): 5 parts; epoxidized soybean oil (epoxy value of 6.5%): 0.3 parts; microcrystalline cellulose (average particle size of 20μm): 0.1 parts. S2. Polyethylene glycol with single-end epoxy groups, polybutylene adipate terephthalate and epoxidized soybean oil are put into a high-speed mixer and premixed at 150 rpm for 40 minutes under nitrogen atmosphere protection at 50°C to obtain premix. The temperature range from the feed port to the die head of the twin-screw extruder was set to 170℃, 175℃, 180℃, 185℃, 190℃, 190℃, 185℃, and 180℃, and the screw speed was 150 rpm. The premixed material, polylactic acid matrix resin, and microcrystalline cellulose were fed into the twin-screw extruder for melt blending. The melt was extruded through the die head, cooled in a water bath, and pelletized to obtain the polylactic acid. Step 2: Preparation of polylactic acid spunlace nonwoven fabric: S1. Spinning: After drying the polylactic acid granules obtained above, they are fed into a melt spinning device for melt spinning. The temperature of the spinning box is set to 190°C. The melt is extruded through a spinneret and cooled by side blowing. The winding speed is 1500 m / min to obtain nascent fibers. The nascent fibers are stretched at 70°C with a stretch ratio of 2.2 times, and then heat-set at 80°C to obtain polylactic acid fibers with a single filament fineness of 2.8 dtex. S2. Web Laying: Polylactic acid fibers are laid into a web using a cross-laying method, with a web weight of 25 g / m². 2 ; S3. Hydroentangling reinforcement: The fiber web is subjected to hydroentangling reinforcement treatment with a hydroentangling pressure of 80 bar. After hydroentangling reinforcement is completed, it is dried under a vacuum of -0.06 MPa until the moisture content is less than 10% to obtain the polylactic acid hydroentangled nonwoven fabric.

[0019] Example 2: This example provides a method for preparing polylactic acid spunlace nonwoven fabric, including the following steps: Step 1: Preparation of polylactic acid: S1. Weigh the raw materials according to the following parts by weight: polylactic acid matrix resin (brand: 4032D, NatureWorks LLC, weight average molecular weight of 200,000, melt flow rate of 12g / 10min at 190℃ and 2.16kg load): 85 parts; polylactic acid-polycaprolactone block copolymer (melting point of 118℃, melt flow rate of 8g / 10min at 190℃ and 2.16kg load): 30 parts; polyethylene glycol-polypropylene glycol block copolymer (NCO-PEG-PPG-NCO, number average molecular weight of 3000) with isocyanate-terminated ends: 20 parts; 2,2'-(1,3-phenylene)-dioxazoline: 2.5 parts; chitin nanofibers (average length of 200nm, average diameter of 20nm): 1.5 parts. S2. Polyethylene glycol-polypropylene glycol block copolymers and polylactic acid-polycaprolactone block copolymers with isocyanate-terminated ends are added to a high-speed mixer and premixed at 350 rpm for 20 minutes under nitrogen atmosphere protection at 80°C to obtain a premix. The temperature range from the feed port to the die head of the twin-screw extruder was set to 170℃, 175℃, 180℃, 185℃, 190℃, 190℃, 185℃, and 180℃, and the screw speed was 350 rpm. The premixed material, polylactic acid matrix resin, and chitin nanocrystals were fed into the twin-screw extruder for melt blending. The melt was extruded through the die head, cooled in a water bath, and pelletized to obtain the polylactic acid. Step 2: Preparation of polylactic acid spunlace nonwoven fabric: S1. Spinning: After drying the polylactic acid granules obtained above, they are fed into a melt spinning device for melt spinning. The temperature of the spinning box is set to 210℃. The melt is extruded through a spinneret and cooled by side blowing. The winding speed is 2800m / min to obtain nascent fibers. The nascent fibers are stretched at 95℃ with a stretch ratio of 3.8 times, and then heat-set at 105℃ to obtain polylactic acid fibers with a single filament fineness of 1.2dtex. S2. Web Laying: Polylactic acid fibers are laid into a web using a cross-laying method, with a web weight of 55 g / m². 2 ; S3. Hydroentangling reinforcement: The fiber web is subjected to hydroentangling reinforcement treatment with a hydroentangling pressure of 120 bar. After hydroentangling reinforcement is completed, it is dried under a vacuum of -0.06 MPa until the moisture content is less than 10% to obtain the polylactic acid hydroentangled nonwoven fabric.

[0020] Example 3: This example provides a method for preparing polylactic acid spunlace nonwoven fabric, including the following steps: Step 1: Preparation of polylactic acid: S1. Weigh the raw materials according to the following parts by weight: polylactic acid matrix resin (brand: 4032D, NatureWorks LLC, weight average molecular weight approximately 150,000, melt flow rate of 20g / 10min at 190℃ and 2.16kg load): 75 parts; polybutylene succinate (melting point 115℃, melt flow rate of 25g / 10min at 190℃ and 2.16kg load): 20 parts; polyethylene glycol with double-ended epoxy groups (number average molecular weight 2000): 12 parts; epoxidized soybean oil (epoxide value 6.5%): 1.4 parts; calcium magnesium phytate (average particle size 5μm): 0.8 parts; S2. Polyethylene glycol and polybutylene succinate with epoxy groups at both ends are put into a high-speed mixer and mixed at 250 rpm for 30 minutes under nitrogen atmosphere protection at 65°C to obtain a premix. The temperature range from the feed port to the die head of the twin-screw extruder was set to 170℃, 175℃, 180℃, 185℃, 190℃, 190℃, 185℃, and 180℃, and the screw speed was 250 rpm. The premixed material, polylactic acid matrix resin, and calcium magnesium phytate were fed into the twin-screw extruder for melt blending. The melt was extruded through the die head, cooled in a water bath, and pelletized to obtain the polylactic acid. Step 2: Preparation of polylactic acid spunlace nonwoven fabric: S1. Spinning: After drying the polylactic acid granules obtained above, they are fed into a melt spinning device for melt spinning. The temperature of the spinning box is set to 200℃. The melt is extruded through the spinneret and cooled by side blowing. The winding speed is 2000m / min to obtain nascent fibers. The nascent fibers are stretched at 85℃ with a stretch ratio of 3, and then heat-set at 95℃ to obtain polylactic acid fibers with a single filament fineness of 2dtex. S2. Web Laying: Polylactic acid fibers are laid into a web using a cross-laying method, with a web weight of 40 g / m². 2 ; S3. Hydroentangling reinforcement: The fiber web is subjected to hydroentangling reinforcement treatment with a hydroentangling pressure of 100 bar. After hydroentangling reinforcement is completed, it is dried under a vacuum of -0.06 MPa until the moisture content is less than 10% to obtain the polylactic acid hydroentangled nonwoven fabric.

[0021] Comparative Example 1 Compared with Example 3, the only difference in the preparation of polylactic acid in Comparative Example 1 is that no polyester elastomer is added.

[0022] Comparative Example 2 Compared with Example 3, the only difference in the preparation of polylactic acid in Comparative Example 2 is that no chain extender is added.

[0023] Comparative Example 3 Compared with Example 3, the only difference in the preparation of polylactic acid in Comparative Example 3 is that no nucleating agent is added.

[0024] Comparative Example 4 Compared with Example 3, the only difference in the preparation of polylactic acid in Comparative Example 4 is that no reactive end-capping hydrophilic agent is added.

[0025] Comparative Example 5 This comparative example provides a method for preparing polylactic acid spunlace nonwoven fabric, including the following steps: Step 1: Preparation of polylactic acid: S1. Weigh the raw materials according to the following parts by weight: polylactic acid matrix resin (brand: 4032D, NatureWorks LLC, weight average molecular weight approximately 150,000, melt flow rate of 20g / 10min at 190℃ and 2.16kg load): 40 parts; polybutylene succinate (melting point 115℃, melt flow rate of 25g / 10min at 190℃ and 2.16kg load): 35 parts; polyethylene glycol with epoxy groups at both ends (number average molecular weight 2000): 25 parts; epoxidized soybean oil (epoxy value 6.5%): 1.4 parts; calcium magnesium phytate (average particle size 5μm): 0.8 parts. S2. Polyethylene glycol and polybutylene succinate with epoxy groups at both ends are put into a high-speed mixer and mixed at 250 rpm for 30 minutes under nitrogen atmosphere protection at 65°C to obtain a premix. The temperature range from the feed port to the die head of the twin-screw extruder was set to 170℃, 175℃, 180℃, 185℃, 190℃, 190℃, 185℃, and 180℃, and the screw speed was 250 rpm. The premixed material, polylactic acid matrix resin, and calcium magnesium phytate were fed into the twin-screw extruder for melt blending. The melt was extruded through the die head, cooled in a water bath, and pelletized to obtain the polylactic acid. Step 2: Preparation of polylactic acid spunlace nonwoven fabric: S1. Spinning: After drying the polylactic acid granules obtained above, they are fed into a melt spinning device for melt spinning. The temperature of the spinning box is set to 200℃. The melt is extruded through the spinneret and cooled by side blowing. The winding speed is 2000m / min to obtain nascent fibers. The nascent fibers are stretched at 85℃ with a stretch ratio of 3, and then heat-set at 95℃ to obtain polylactic acid fibers with a single filament fineness of 2dtex. S2. Web Laying: Polylactic acid fibers are laid into a web using a cross-laying method, with a web weight of 40 g / m². 2 ; S3. Hydroentangling reinforcement: The fiber web is subjected to hydroentangling reinforcement treatment with a hydroentangling pressure of 100 bar. After hydroentangling reinforcement is completed, it is dried under a vacuum of -0.06 MPa until the moisture content is less than 10% to obtain the polylactic acid hydroentangled nonwoven fabric.

[0026] Performance testing: (1) Fiber performance testing: Referring to standard GB / T14344-2022, the monofilament strength and monofilament elongation of polylactic acid fibers prepared in Examples 1-3 and Comparative Examples 1-5 were determined using a single fiber strength tester. The test results are shown in Table 1: Table 1

[0027] As shown in Table 1, the polylactic acid fiber prepared by this invention has high strength and good toughness. Compared with Example 3, in Comparative Example 1, the absence of polyester elastomer led to a significant decrease in fiber toughness and strength. Polyester elastomer, as a flexible segment in the system, can effectively absorb and disperse stress. Its inherent flexible segments and polylactic acid matrix form a chemical bond interface through the bridging effect of the chain extender, significantly improving the fiber's toughness and strength. When the polyester elastomer is absent, the material exhibits brittle fracture characteristics, and the elongation drops sharply. In Comparative Example 2, the absence of the chain extender led to a significant decrease in both fiber strength and elongation. The multifunctional active groups in the chain extender molecule can react simultaneously with polylactic acid, hydrophilic agent, and elastomer to form a chemical bond grafting network, increasing the entanglement density and interfacial bonding strength between molecular chains. When the chain extender is absent, an effective chemical cross-linking network cannot be formed between the components, reducing stress transfer efficiency and leading to deterioration of mechanical properties. In Comparative Example 3, the absence of nucleating agent leads to a decrease in fiber performance. Nucleating agent promotes heterogeneous nucleation of polylactic acid during spinning and cooling, forming a finer and more uniform crystal structure, which improves the initial modulus and strength of the fiber. When nucleating agent is absent, polylactic acid crystallization is insufficient and the grains are coarse, resulting in a slight decrease in strength. In Comparative Example 4, the absence of reactive end-capping hydrophilic agent leads to a significant decrease in fiber elongation. Reactive hydrophilic agent reacts chemically with polylactic acid and chain extender through the terminal epoxy or isocyanate groups, and is incorporated into the polymer network in a covalent manner. Its polyethylene glycol segments have flexibility, which helps to improve the flexibility of polymer segments. When reactive hydrophilic agent is absent, although the decrease in strength is limited, the loss in toughness is obvious. In Comparative Example 5, the low content of polylactic acid matrix resin leads to insufficient continuous phase in the material. Although the high content of elastomer and hydrophilic agent results in a high elongation, the strength decreases significantly.

[0028] (2) Performance testing of nonwoven fabrics: The polylactic acid spunlace nonwoven fabrics prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to performance testing. The dry and wet strength of the nonwoven fabrics were determined according to standard GB / T24218.3-2010, the softness of the nonwoven fabrics was determined according to standard GB / T8942-2016, and the liquid penetration time of the nonwoven fabric samples was determined according to EDANA10.3-02. The test results are shown in Table 2. Table 2

[0029] As shown in Table 2, the nonwoven fabric prepared by this invention has high strength, high softness, and good hydrophilicity. Compared with Example 3, in Comparative Example 1, the absence of polyester elastomer led to a significant decrease in the dry and wet strength of the nonwoven fabric, especially the wet strength attenuation was more severe, and the softness was significantly deteriorated. The polyester elastomer forms a chemical bond interface with polylactic acid through the bridging effect of the chain extender, which effectively promotes stress dispersion and energy absorption, so that the material can improve toughness without sacrificing mechanical integrity. The absence of elastomer also led to a decrease in the flexibility of the inter-fiber entanglement structure, affecting the hydroentangling reinforcement effect, and thus leading to a more significant loss of wet strength. In Comparative Example 2, the absence of chain extender led to a significant decrease in the dry and wet strength of the nonwoven fabric. The strength decreases, the softness deteriorates, and the hydrophilicity worsens. The multifunctional active groups of the chain extender can react simultaneously with polylactic acid, hydrophilic agents, and elastomers to form a chemically bonded graft network, anchoring hydrophilic segments covalently in the matrix and enhancing interfacial bonding. When the chain extender is missing, an effective chemical cross-linking network cannot be formed between the components, leading to easy migration and loss of the hydrophilic agent, weakened interfacial bonding, and a decrease in both mechanical properties and hydrophilic durability. In Comparative Example 3, the absence of the nucleating agent has a relatively small impact on the performance of the nonwoven fabric, but it still affects strength and hydrophilicity. The nucleating agent is present during the spinning cooling process. During the hydroentangling process, the nonwoven fabric promotes heterogeneous nucleation of polylactic acid, forming a finer and more uniform crystal structure, which improves the initial modulus and strength of the fiber. This, in turn, affects the impact resistance of the fiber during hydroentangling and the uniformity of the final fabric surface. When the nucleating agent is missing, the fiber crystallization is insufficient, the strength decreases slightly, and the overall performance of the nonwoven fabric deteriorates slightly. In Comparative Example 4, the absence of reactive end-capping hydrophilic agent has a significant impact on the hydrophilicity of the nonwoven fabric, and also has a significant impact on the wet strength. The epoxy or isocyanate groups at the end of the reactive hydrophilic agent react chemically with polylactic acid and chain extender, anchoring them covalently to the fiber. In the polymer matrix, the migration and precipitation of hydrophilic components in an aqueous environment are fundamentally avoided, giving the material durable and stable hydrophilicity. When the reactive end-capping hydrophilic agent is missing, the nonwoven fabric loses its source of hydrophilicity, and the liquid penetration time is greatly extended. At the same time, the lack of network structure involving hydrophilic agents also leads to a decrease in wet strength. In Comparative Example 5, the low content of polylactic acid matrix resin leads to insufficient continuous phase in the material. Although the high content of elastomer and hydrophilic agent makes the softness better, the dry strength and wet strength are seriously insufficient, especially the wet strength is reduced by more than half, which cannot meet the strength requirements of soft wet wipes.

[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A polylactic acid, characterized in that, It is prepared by weight of the following components: 60-85 parts polylactic acid matrix resin, 10-30 parts polyester elastomer, 5-20 parts reactive end-capping hydrophilic agent, 0.3-2.5 parts chain extender, and 0.1-1.5 parts nucleating agent.

2. A method for preparing polylactic acid as described in claim 1, characterized in that, Includes the following steps: The reactive end-capped hydrophilic agent, the polyester elastomer, and the chain extender are premixed to obtain a premix; The premixed material is melt-blended with the polylactic acid matrix resin and the nucleating agent, and then extruded, cooled, and pelletized to obtain the polylactic acid.

3. The method for preparing polylactic acid according to claim 2, characterized in that, The polyester elastomer is selected from at least one of polybutylene adipate-terephthalate, polylactic acid-polycaprolactone block copolymer, and polybutylene succinate. The melting point of the polyester elastomer is 80-120℃, and the melt flow rate is 5-50g / 10min at 190℃ and 2.16kg load.

4. The method for preparing polylactic acid according to claim 2, characterized in that, The reactive end-capping hydrophilic agent is selected from at least one of the following: polyethylene glycol with a single end capped with an epoxy group, polyethylene glycol with a single end capped with an isocyanate group, polyethylene glycol-polypropylene glycol block copolymer with a single end capped with an epoxy group, polyethylene glycol-polypropylene glycol block copolymer with a single end capped with an isocyanate group, polyethylene glycol with two ends capped with epoxy groups, polyethylene glycol with two ends capped with an isocyanate group, polyethylene glycol-polypropylene glycol block copolymer with two ends capped with an epoxy group, and polyethylene glycol-polypropylene glycol block copolymer with two ends capped with an isocyanate group. The number average molecular weight of the reactive end-capped hydrophilic agent is 1000-3000.

5. The method for preparing polylactic acid according to claim 2, characterized in that, The chain extender is selected from at least one of epoxy chain extenders and oxazoline chain extenders.

6. The method for preparing polylactic acid according to claim 2, characterized in that, The nucleating agent is selected from at least one of microcrystalline cellulose, calcium magnesium phytate, and chitin nanocrystals.

7. The method for preparing polylactic acid according to claim 2, characterized in that, The premixing conditions are as follows: mixing for 20-40 minutes at 50-80°C under nitrogen atmosphere protection; during melt blending, the processing temperature range is 170-190°C and the screw speed is 150-350 rpm.

8. A polylactic acid spunlace nonwoven fabric, characterized in that, It is prepared by spinning, web laying and hydroentangling of polylactic acid as described in claim 1, specifically including: S1. Spinning: After drying the polylactic acid, polylactic acid fibers are obtained through melt spinning, winding, stretching and heat setting processes. S2, Web Laying: Laying polylactic acid fibers into a web; S3. Hydroentangling reinforcement: The fiber web is subjected to hydroentangling reinforcement treatment and dried to obtain the polylactic acid hydroentangled nonwoven fabric.

9. The polylactic acid spunlace nonwoven fabric according to claim 8, characterized in that, In step S1, the spinning temperature is 190-210℃, the winding speed is 1500-2800m / min, the drawing temperature is 70-95℃, the draw ratio is 2.2-3.8 times, the heat setting temperature is 80-105℃, and the polylactic acid fiber monofilament fineness is 1.2-2.8 dtex. In step S2, the web is laid in a cross-lay method, and the web weight is 25-55 g / m². 2 In S3, the hydroentangling pressure is 80-120 bar.

10. An application of polylactic acid spunlace nonwoven fabric as described in claim 8 or 9 in soft wet wipes.

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